NASA’s Troubled $8-Billion Hubble Successor Is Back on Track

The Hubble Space Telescope is still operating, but its successor is already waiting in the wings. The James Webb Space Telescope (JWST) will be the largest observatory ever sent to space, and one of the most complex instruments ever built. After running seriously over budget and behind schedule until 2011, the project is now on track and heading into an eventful year of assembly and tests in preparation for its 2018 launch.
 
All four of the JWST's main science instruments are built and have been shipped to the NASA Goddard Space Flight Center in Greenbelt, Md., to be combined into one unit, called the Integrated Science Instrument Module (ISIM). Last month the telescope passed its final design milestone—the critical design review—where all of the plans for design, construction and testing of the observatory were approved. "Ninety-seven percent of the mass of the telescope is either built or on the way," Eric Smith, JWST deputy program director at NASA Headquarters in Washington, D.C., said during a January press tour of Goddard. "Now [that] we've got the science instruments, we're going to start manufacturing the telescope."